I need to buy a mirror for ridding. bought one from my LBS but I don't like it. It is a helmet mirror and I don't seem to be using it right or something. I set it before I ride but all it seems to p/u when I rode is my back pack. I think since I was trying to save a buck it just maybe that it is cheap. I own more than one bike so I would prefer a helmet or glasses mount style. Which do you all find better? Can the glasses mount be interchanged?I own more than one set of specs. And finally is there a peticular brand that is better?